Field of the Invention
This invention relates to an image sensing apparatus and to a method, of controlling this apparatus.
Description of the Related Art
In the special effects function of digital cameras and in the production of TV commercials, the general practice is to execute image processing in which, by leaving only a specific color intact and changing the other colors to gray, an effect is obtained, in which attention is drawn to the portion having the specific color. In image processing of this kind, it is possible to change to gray the colors outside of a pre-registered range of colors if the color distribution of the portion desired to be noticed is already known. However, in a case where a photographic subject has not been decided as in a digital camera, it is necessary to devise a method of setting the specific color.
It is comparatively easy to change to gray colors other than a specific color by having the user designate one candidate from among several specific color candidates (such as red, yellow and blue) the chromaticity range of which is predetermined, or by having the user designate a portion of the image of a subject.
Further, there is a technique in which a specific color area is decided with regard to a subject in which a relationship with respect to average luminance can be modeled as in the manner of the color of skin or the color of the sky (Patent Document 1), a technique for extracting the color information at a designated position in an image and converting the region corresponding to this color information to another color (Patent Document 2), and a technique for acquiring the color distribution of a subject by preparatory shooting using a provisional background and then changing the background at the time of actual shooting of the subject (Patent Document 3).
Patent Document 1: WO 2006/059573
Patent Document 2: Japanese Patent Application Laid-Open No. 7-320024
Patent Document 3: Japanese Patent Application Laid-Open No 2002-118859
When graying colors, other than a designated color, it is necessary to re-designate the specific color and to re-shoot if the result of graying is not satisfactory. This complicates operation. Further, obtaining satisfactory results takes a great deal of time. Furthermore, processing for graying the image of a moving subject is extremely difficult.
Further, according to the description set forth in Patent Document 1, since the target is a subject in which the relationship with respect to average luminance is capable of being modeled in advance, this technique cannot be applied to a unspecified subject. According to the description set forth in Patent Document 2, an operation for designating a position at which color information is extracted from within an image and verification of the results of the conversion are required to be repeated. Furthermore, according to the description set forth in Patent Document 3, the technique cannot be used for general subjects in which the background cannot be set.